1. Field of the Invention
The present invention relates to clamps which frictionally and releasibly engage two axially aligned pipes to prevent forced separation of the pipes. More specifically, the present invention relates to a sewer line vent clamp assembly having a novel double circumferential ribbing for effectively gripping thin-walled polyvinylchloride (PVC) tubing, and releasibly fixing a thin-walled PVC pipe to a standard, flared sewer trap. The present invention effectively connects a PVC vent pipe to a sewer trap without piercing or distorting the thin wall of the PVC vent pipe.
2. Description of the Prior Art
As shown in the patent literature, frictional clamp assemblies for spanning the connection between two axially connected pipes have been patented in the past. In some cases, the clamp assemblies are only temporarily positioned about the pipes to immobilize them while a primary joint between the two pipes is made (as, for instance, by welding). In other cases, the clamp assemblies are designed to remain in place about the pipes even after the primary joining of the two pipes has been completed. The configurations of these various prior art pipe clamps differ according to the type of pipe which is being joined, e.g., glass, ceramic, metal; end-to-end abutting connection, male-female connection, etc.
U.S. Pat. No. 4,336,959, issued Jun. 29, 1982, to Charles Roche describes a restrainer for a joint in plastic conduit. The device includes a solid "retainer" ring, and a "clamping" ring which are drawn together by bolts. The clamping ring consists of two semi-circular elements which are biased about the periphery of one of the pipes being joined by bolts passing through end flanges in each of the semi-circular elements. At least one of the pipes being joined by this device must have an annular, outwardly extending "corrugation" at the end which abuts the joint to the other pipe. The diameter of the corrugation must be larger than the inside diameter of the solid retainer ring. In operation, the solid retainer ring is then slipped over the other end of the corrugated pipe, and biased against the corrugation. The clamping ring is then fitted to another pipe (depicted as a smooth pipe in FIG. 1), and the two pipes are biased to one another by longitudinal bolts passing through both the retainer ring and the clamping ring. As is shown in the drawings, this device relies on the corrugation of at least one of the pipes to maintain the solid retainer ring in place. Clearly, this device cannot be used to join two smooth pipes because there would be no means to keep the solid ring fastened about one of the pipes
A reinforced high temperature glass conduit is described in U.S. Pat. No. 2,606,574, issued Aug. 12, 1952, to Lefebvre. FIG. 3 of this patent depicts a conventional pipe clamp assembly for joining two flared-end glass tubes in end-to-end abutment. The pipe clamp assembly includes two identical halves, each having two semi-circular elements releasibly fastened around the circumference of a pipe. The two halves, along with the pipes to which they attached, are then biased toward one another using longitudinal bolts. No ribbing of any sort is shown on the inside diameter of either of the two halves of the assembly.
U.S. Pat. No. 3,252,192, issued May 24, 1966, to Joseph B. Smith, discloses a frictional clamp ring assembly for connecting axially disposed pipes. In identical fashion to the Lefebvre apparatus, above, Smith describes a pipe clamp apparatus having two identical halves, each half consisting of two semi-circular elements biased together by bolts. The two halves, and the pipes to which they are attached, are then biased together by longitudinal bolts. The frictional engagement of the semi-circular elements onto the pipes is enhanced by an epoxy coating interposed between the inner diameter of the semi-circular elements and the surface of the pipe being clamped. To further increase the attachment of the entire assembly to the pipe joint, a material filler having a hardness greater than that of the pipes themselves, preferably steel shot, is incorporated into the epoxy. No ribbing of any sort is shown on the inside diameter of either of the two halves of the assembly. A major drawback to this device is that the epoxy layer permanently fixes the clamp assembly to the joined pipes. Should one or both of the pipes require replacement, it would be a very difficult matter to remove the clamp assembly from the pipe to be replaced. Also, this invention is not particularly suitable for application to PVC pipe because the steel shot contained within the epoxy would penetrate a great distance into a comparatively soft PVC pipe, thereby greatly weakening it.
U.S. Pat. No. 4,026,586, issued May 31, 1977, to Harold Kennedy, Jr. et al, discloses a plain end pipe joint assembly in which a corrugated sleeve of material is wrapped about the ends of two pipes. The sleeve is then tightened via bolts to join the two pipe ends together. A non-corrugated shim sleeve may be interposed between the corrugated sleeve and the pipes to ensure a better seal at the joint. However, since Kennedy's corrugations are blunt, and are positioned parallel with the longitudinal axis of the pipe, this device is less effective in preventing longitudinal separation of the pipes relative to each other compared to the strong fit of the present invention, which includes a plurality of circumferentially arranged ribs positioned perpendicularly to the longitudinal axis of the pipe joint.
U.S. Pat. No. 4,635,970, issued Jan. 13, 1987, to Robert E. Haines, discloses a thrust anchor apparatus for strengthening and stabilizing joints in water supply pipes against the forces exerted on the pipes by water flowing through them. The Haines reference describes an anchor system which incorporates two clamps, each of which is welded onto a pipe adjacent to the end being connected. Rod-like members are used to urge the clamps, and the pipes to which they are welded, together. As noted above, the disadvantage of fixedly attaching the clamps to the pipes is that the pipes themselves cannot be replaced without also replacing the anchoring apparatus.
U.S. Pat. No. 4,865,298, issued Sep. 12, 1989, to Peter Jordan, discloses a tuyere stock for blast furnaces which exemplifies a type of clamping assembly utilized when a connection between two pipes is displaceable in an axial direction.
An example of a pipe coupling or clamp having a non-planar inner surface is shown in U.S. Pat. No. 4,896,902, issued Jan. 30, 1989, to Richard S. Weston. The Weston pipe coupling device allows for pipes having differing outer diameters to be connected in axial alignment with one another. This device consists of a single clamp assembly having two semi-circular halves. The two halves are releasibly fastened together by bolts passing through flanges in each half.
U.S. Pat. No. 5,090,742, issued Feb. 25, 1992, to Jack L. Cohen et al, and U.S. Pat. No. 5,161,828, issued on Nov. 10, 1992, to Joseph H. Hynes et al, further represent the state of the art regarding pipe clamps which span two pipes already joined by a primary connector. Cohen et al also describes using a liner between the clamp and the pipe to ensure a snug fit between the pipe and the clamp itself.
None of the above patent references, taken alone or in any combination, is seen as anticipating or fairly suggesting the presently claimed invention.